This invention relates to an ink composition having high storage stability for use in heat transfer printing of fiber products including textiles and fabrics, particularly those of acid-modified synthetic fibers.
Heretofore, a process for heat transfer printing acid-modified synthetic fiber products, such as acrylic fiber and polyester fiber products dyeable with cationic dyes, with basic dyes (cationic dyes) has been widely known as the heat transfer or sublimation transfer process.
Since this process resorts largely to the heat transferability of dyes (which is due mainly to sublimation, but may also be caused by melting and evaporation in some cases), various processes for increasing the heat transferability of the basic dyes have been proposed. One of such processes is a process wherein a basic dye is used with a base thereby to increase the sublimability of the dye (for instance, Japanese Patent Laid-Open Nos. 12916/1974 and 12917/1974), and another example of proposed processes is a process wherein a basic dye is converted to a carbinol base thereof or its derivative and then is used as a dye for transfer printing (for instance, Japanese Patent Laid-Open Nos. 18784/1975 and 14889/1975).
Dyes with increased heat transferability obtained in the above described manner are advantageous from the viewpoint of heat transfer printing procedures, but are very disadvantageous when ink compositions containing such dyes and transfer sheets obtained by using the same are stored because their storage stability is reduced by the increased heat transferability of the dyes.
For example, in the case of such an ink composition, the dye contained therein will deteriorate or decompose during storage, and a transfer sheet or a transferred pattern obtained by using an ink composition stored for 1 or 2 months after preparation will be reduced in concentration and changed in hue in comparison with that obtained by using the same ink composition freshly prepared. These tendencies are particularly notable in some dyes.
The aforementioned defects in the conventional ink compositions for heat transfer printing have been considered to be due to the instability of carbinol bases or their derivatives which are easily transferable dyes (see, for example, Japanese Patent Laid-Open No. 86691/1974 and "Dyeing Industry", 24(4), pp. 33-46).
Since transfer printers are not ordinarily the same as transfer sheet or transfer printing ink makers, reduction in storage stability decreases the commercial value of transfer sheets or inks for transfer printing to a great extent.